Recently, in moving into the aging society, there have been developed various kinds of appliances which can be easily handled by a user and in which such information relating to the living body as is required for healthcare can be easily obtained. As an example of this kind of appliances, there is known an ultrasound probe for measuring, by using a pulse-echo method, the diameter of blood vessel of a wrist radius artery. As the ultrasound probe, the mainstream is a wearable and flexible array type in which a plurality of piezoelectric elements as function elements for transmitting/receiving ultrasound are disposed in an array shape (see, for example, Patent Document 1). By disposing a plurality of piezoelectric elements in the array shape in this manner, without the necessity of relying on specialists such as clinical doctors, clinical engineers, and the like, the user may attach the product thus obtained to the skin on the wrist radius artery so that the expansion and contraction of the artery radius can be measured by the ultrasound and converted into blood pressure. In addition, by measuring the pulsation of the blood vessels, without being limited to the measuring of the blood pressure, not only the measurements of the brain waves and heart rates, but also the evaluation of hardness of the blood vessels can be evaluated from the change with time of the expansion and contraction of the blood vessels. As a result, it becomes possible to routinely monitor the diseases of the blood vessels such as arterial sclerosis and cardiac disease. It is expected, out of the correlation with the vascular endothelial disorders, to apply the measurements to the prevention and care of hypertension and diabetes.
In the above-mentioned conventional examples, grooves are formed on a block-shaped piezoelectric composite having a predetermined thickness by using a dicing machine; an electrically insulating resin is filled into the grooves thus formed; and thereafter both main surfaces in the thickness-wise direction are respectively polished by a polishing apparatus. Then, on both the main surfaces of the piezoelectric composite, divided electrodes and overall electrodes are respectively formed by a sputtering method or a plating method. In this manner, there is manufactured a product in which each of the piezoelectric elements to transmit/receive ultrasound is arranged in an array shape at a certain interval.
It is known that the piezoelectric ceramics such as PZT and barium titanate, and piezoelectric composite constituted by piezoelectric single crystal such as PMN-PT and the like will have the oscillatory frequency determined depending on their thicknesses. In this case, for example, in case PMM-PT is used as the piezoelectric element for an ultrasound probe which transmits/receives ultrasound, the characteristics will be impaired even by the change in thickness by several μm. Therefore, in a manufacturing method such as of the above-mentioned prior art in which, in order to divide into respective piezoelectric elements, resin is filled and the main surface is polished, it will be difficult to make the thickness of each of the piezoelectric elements to coincide with one another. Still furthermore, there will arise a problem in that the transmitting frequency of each of the piezoelectric elements cannot be made uniform. In this case, only those piezoelectric elements which have different transmitting frequencies can neither be replaced out of each of the piezoelectric elements arranged in an array shape. It is therefore an urgent problem to develop a structure of a device and the method of manufacturing the device, with a good yield rate, in which a plurality of function elements having a uniform thickness are disposed in an array shape at predetermined intervals.